The method used to stun farmed salmon before slaughter has significant welfare implications for billions of fish annually. Electrical stunning is increasingly recognized as more humane than CO2 or live chilling.
The welfare of farmed salmon at slaughter depends critically on the stunning method used. CO2 exposure — historically common because of its low cost and scalability — causes aversive reactions as fish attempt to escape the gas-saturated water, experiencing hyperventilation and apparent distress for seconds to minutes before losing consciousness. Electrical stunning, applied via water bath or percussive device, renders fish insensible rapidly and with minimal avoidance behavior. The evidence that fish experience pain and stress is now mainstream — the EFSA's formal conclusion that CO2 is unacceptable for salmon represents a significant regulatory milestone. Where electrical stunning is adopted, welfare at slaughter can approach or match standards achievable for terrestrial livestock. The challenge is consistent implementation across the full supply chain, including small producers in developing regions.